Rings of Saturn
with it magnificent rings, is the sixth planet from the
the wonders of the solar system, none are quite as amazing as
the rings of Saturn. Saturn, the second largest planet in our
solar system, is not the only world with rings - Jupiter, Uranus
and Neptune have some too - but Saturn's are by far the most visible
man had watched the sky for thousands of years, it wasn't until
1610 A.D. that Italian scientist Galileo Galilei first noticed
Saturn's rings while using a new invention called the telescope.
At first Galileo wasn't sure of what he was seeing and thought
that Saturn wasn't just a single object but one with two smaller
objects on either side. The "planet Saturn is not alone, but is
composed of three, which almost touch one another and never move
nor change with respect to one another," he wrote. Later he described
the planet as having "ears". Even more puzzling was when he looked
at it again in 1612; the "ears" had disappeared only to reappear
again to him in 1613.
Circles the equator of the Saturn, the 6th planet from
Ranges from 30 feet (10m) to 3,200 feet (1km).
174,208 miles (280360 km).
of: Millions of particles which are 99.9% made of ice with
traces of minerals.
By Galileo Galilei in 1610 A.D.
Composed of at least a dozen smaller rings separated by
The rings can't be seen from Earth every 14 years because
they turn on edge toward us.
another scientist, Christiaan Huygens, using a more powerful telescope
in 1655 to figure out that what Galileo had seen were not two
objects on either side of the planet, but a ring surrounding it.
Why had it disappeared in 1612? As Saturn orbits the sun, its
angle changes when observed from earth. During 1612 the rings,
which are very narrow, were facing Earth edge on, and disappeared
from sight. They reappeared in 1613 as the angle of the planet
continued to change when it moved further along in its orbit.
Today we know that we can expect the rings of Saturn to vanish
from view as they turn edge on about every 14 years.
astronomer Giovanni Domenico Cassini noticed that the ring wasn't
solid, but composed of multiple rings with gaps. The largest of
these separations was named the Cassini gap in his honor. James
Clerk Maxwell calculated in 1859 that the rings could not be solid
objects because the gravitational forces imposed on them would
rip them apart. He speculated they were actually composed of millions
of small particles, all in their own orbit around Saturn. This
theory was confirmed in 1895 by spectroscopic studies of the rings
through the telescope at the Allegheny Observatory which is part
of the University of Pittsburgh.
Italian scientist Galileo Galilei first discovered the rings
of Saturn while looking through the newly invented telescope
done with modern telescopes and space probes show that there are
at least a dozen concentric rings circling Saturn. Most of them
are designated by letters in the order in which they were discovered
(For example, the Cassini gap is bordered by the A and B rings).
The portion of the ring system easily visible from Earth's telescopes
starts at the D ring about 41,570 miles (66,900 km) from Saturn's
center and runs to the F ring at 87,104 miles (140,180km). This
is a distance of 45,534 miles (73,280km) or about 5½ times the
diameter of the earth. Diffuse and invisible parts of the rings
composed mainly of dust, however, can be detected as far away
as 8 million miles (13,000,000km) from the planet's center.
the visible part of the rings has a diameter of 174,208 miles
(280360 km) which is about ¾ the distance between the earth and
the moon, the width of the rings only ranges between 30 feet (10m)
and 3,200 feet (1km). Despite the huge area of the rings, they
are not very dense and the amount of actual material they are
composed of is relatively small. If it was all gathered together
in one place it is estimated it might be the volume of one of
Saturn's medium-sized moons like Mimas, which has a diameter of
246 miles (396km).
of the rings show that they are about 99.9 percent composed of
ice with just a trace of minerals. The particles that make up
the rings range from the size of a pebble to the size of a small
house. Photos from space probes have shown that within the rings
themselves complex patterns can appear that make it look like
a ring is braided. The rings and patterns in the rings are probably
caused by the gravitational interaction of Saturn and its many
moons. Several tiny "Shepherd moons" orbit within the rings creating
some of the gaps. For example, the F ring is maintained by the
moons Prometheus on its inner edge and Pandora on its outer edge.
close up of Saturn's rings with major rings labeled. The
Cassini gap is bordered by the A and B rings. (NASA)
are several theories about how the rings came to be. In the 19th
century French astronomer and mathematician Édouard Roche proposed
that the rings were the remains of a large moon of Saturn's that
had been ripped apart. Using math, he calculated how close a moon
could get to its mother planet before the planet's gravitational
tidal forces would tear it to pieces. This rule, now known as
the Roche limit, can be calculated for any celestial object.
The rings fall within Saturn's Roche limit.
idea that an existing moon had been drawn close to Saturn, then
been broken up was an early theory, but not the only one. Another
theory is that the rings are composed of matter left over from
original material from which Saturn formed. Material outside the
Roche limit was eventually drawn together under its own gravity
into clumps that formed Saturn's moons, while material inside
the limit spread out to make rings. Another variation of Roche's
theory is that an existing moon was struck by a large comet or
asteroid, which caused it to break apart into small pieces and
form the rings.
the 1980's everything astronomers knew about the rings was learned
from Earth-based telescopes. During that decade, however, two
space probes, Voyager 1 and 2, swept by Saturn and took a number
of high resolution photos of the rings. More recently, in 2005,
the Cassini-Huygens probe (named after two 17th century astronomers)
actually passed though the rings at the gap between the F and
G rings. It continues to operate in the vicinity of Saturn, returning
photos and other observations about Saturn, its moons, and rings
to scientists on Earth.
aren't exactly sure how long the rings have been circling Saturn.
One recent estimate, however, based on data from the Cassini probe,
puts their age at around 4 billion years, about the same age as
the rest of the solar system.
we don't know exactly how they formed or how old they are, one
thing about the rings is certain. They are of surpassing beauty
and a wonder of our solar system.
artist's conception of the view from inside a ring. (NASA).
2013 Lee Krystek. All Rights Reserved.